打开卡片视图时如何获取特定用户的数据

Question

I search a user based on the name or email and click on that card view. I want the screen to display the user's data from firebase. How do I get that user's Id based on that? I used a bundle but I am getting an error.

Here is my code for the individual page.

public class UserSingleActivity extends AppCompatActivity {
    private Button btnsendFriendRequest;
    private TextView displayName,displayEmail,displayId;
    private DatabaseReference mUserDatabase;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_user_single);

        //.....

        //Here is the error
        String userId=getIntent().getExtras().getString("userId");//look for the user Id

        mUserDatabase= FirebaseDatabase.getInstance().getReference().child("users").child(userId);

        mUserDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                String display_name=dataSnapshot.child("name").getValue().toString();
                String display_email=dataSnapshot.child("email").getValue().toString();
                displayName.setText(display_name);
                displayEmail.setText(display_email);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }
}

Here is the viewHolder.

public class FriendsViewHolders extends RecyclerView.ViewHolder implements View.OnClickListener {

    private DatabaseReference userDB;
    public TextView name,email,userId;

    public FriendsViewHolders(@NonNull View itemView) {
        super(itemView);
        itemView.setOnClickListener(this);

        name = (TextView)itemView.findViewById(R.id.name);
        email = (TextView)itemView.findViewById(R.id.email);

    }
    @Override
    public void onClick(View v) {
        Intent intent=new Intent(v.getContext(), UserSingleActivity.class);
        v.getContext().startActivity(intent);

    }
}

Here is the error.

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
        at com.example.android.myapplication.UserSingleActivity.onCreate(UserSingleActivity.java:29)

Answer 1

You are trying to access a value that hasn't been previously saved in the bundle. Before starting the activity, you should use something like:

intent.putExtra("userId", name.getText().toString());

Or instead of name.getText().toString(), you should put the name you will load from the other class. This would save the value and you should be able to access it later.

Hope it helps!

Answer 2

mUserDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                String display_name=dataSnapshot.child("name").getValue().toString();
                String display_email=dataSnapshot.child("email").getValue().toString();
                displayName.setText(display_name);
                displayEmail.setText(display_email);
            }

from above code when you're doing

String display_name=dataSnapshot.child("name").getValue().toString();
                String display_email=dataSnapshot.child("email").getValue().toString();

send this to other classAdapter where you're putting to show.